{"gene":"H2AX","run_date":"2026-04-28T18:06:53","timeline":{"discoveries":[{"year":1998,"finding":"DNA double-strand breaks induce rapid phosphorylation of histone H2AX specifically at serine 139 (forming γ-H2AX), with approximately 2×10⁶ base pairs of chromatin involved per DSB, indicating large-scale chromatin domain modification at each break site.","method":"Two-dimensional gel electrophoresis, 32P incorporation, in vivo phosphorylation assays in irradiated mammalian cells and mice","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — original discovery with multiple orthogonal biochemical methods, foundational paper with 4387 citations","pmids":["9488723"],"is_preprint":false},{"year":2001,"finding":"ATM is the major kinase responsible for H2AX phosphorylation at serine 139 in response to DSBs; ATM phosphorylates H2AX in vitro, H2AX phosphorylation is severely compromised in ATM-/- cells, and ectopic ATM expression in ATM-/- cells restores H2AX phosphorylation. DNA-PK accounts for residual phosphorylation in the absence of ATM.","method":"In vitro kinase assay, ATM-/- and DNA-PKcs-/- cell lines, rescue by ectopic ATM expression, wortmannin inhibition","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — in vitro kinase assay plus genetic knockouts plus rescue experiment, replicated across labs","pmids":["11571274"],"is_preprint":false},{"year":2004,"finding":"ATM and DNA-PK function redundantly to phosphorylate H2AX after ionizing radiation; ablation of both kinases is required to eliminate IR-induced H2AX phosphorylation. ATR is not involved in H2AX phosphorylation in non-replicating cells. DNA-PK-mediated H2AX phosphorylation contributes to recruitment of MDC1 and 53BP1 to DSB sites.","method":"ATM-deficient cells treated with LY294002 (DNA-PK inhibitor); ATM/DNA-PK double-deficient chicken cells; epistasis analysis","journal":"Cancer research","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis with pharmacological inhibition, replicated in multiple cell systems","pmids":["15059890"],"is_preprint":false},{"year":2002,"finding":"H2AX is required for efficient G2-M checkpoint activation after low doses of ionizing radiation; H2AX-/- mice show a G2-M checkpoint defect comparable to ATM-/- cells. H2AX regulates the efficient accumulation of 53BP1 into IR-induced foci, thereby amplifying the damage signal at threshold DSB levels.","method":"H2AX-/- and 53BP1-/- mouse genetic knockouts, flow cytometry cell cycle analysis, immunofluorescence for 53BP1 foci","journal":"Nature cell biology","confidence":"High","confidence_rationale":"Tier 2 — clean genetic knockout with specific cellular phenotype, multiple readouts","pmids":["12447390"],"is_preprint":false},{"year":2003,"finding":"53BP1 directly binds phosphorylated H2AX (but not unphosphorylated H2AX) through a region upstream of its C-terminus; H2AX phosphorylation at serine 139/140 is required for efficient 53BP1 foci formation at DNA breaks. Hyperphosphorylation and relocalization of 53BP1 occur independently.","method":"In vitro binding assays, H2AX-deficient cells reconstituted with wild-type or phosphorylation-deficient H2AX mutants, immunofluorescence","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 — in vitro binding assay plus genetic reconstitution with phosphorylation mutants","pmids":["12697768"],"is_preprint":false},{"year":2003,"finding":"H2AX functions as a dosage-dependent suppressor of genomic instability and tumors; H2AX haploinsufficiency causes genomic instability in normal cells. Restoration of H2AX null allele with wild-type H2AX restores genomic stability and radiation resistance, but substitution of the conserved serine phosphorylation sites (S→A or S→E) abolishes this rescue, demonstrating phosphorylation-dependence.","method":"Gene targeting (H2AX-/- and H2AX+/- mice), p53-/- double knockouts, transgenic reconstitution with phosphorylation-site mutants, cytogenetic analysis","journal":"Cell","confidence":"High","confidence_rationale":"Tier 2 — genetic knockouts with site-specific mutant rescue, replicated independently in two concurrent Cell papers","pmids":["12914701","12914700"],"is_preprint":false},{"year":2004,"finding":"The INO80 chromatin remodeling complex is recruited to DSBs through a direct interaction with γ-H2AX (phosphorylated H2AX); this interaction requires the Nhp10 HMG-like subunit of INO80. Loss of Nhp10 or γ-H2AX reduces INO80 recruitment to DSBs, linking ATP-dependent chromatin remodeling to DNA repair.","method":"Co-immunoprecipitation, chromatin immunoprecipitation at HO endonuclease-induced DSB in yeast, genetic epistasis with RAD52 pathway","journal":"Cell","confidence":"High","confidence_rationale":"Tier 2 — reciprocal Co-IP, ChIP, genetic epistasis in yeast ortholog system","pmids":["15607974"],"is_preprint":false},{"year":2004,"finding":"BRCA1 is required for recruiting ATR kinase to XY chromatin at the onset of meiotic sex chromosome inactivation (MSCI); ATR then phosphorylates H2AX within the XY body, triggering chromatin condensation and transcriptional repression of sex chromosomes.","method":"Immunofluorescence localization of ATR in wild-type vs. BRCA1-mutant pachytene spermatocytes, correlation of ATR localization with H2AX phosphorylation and MSCI","journal":"Current biology : CB","confidence":"High","confidence_rationale":"Tier 2 — direct localization experiment with functional consequence in genetic mutant background","pmids":["15589157"],"is_preprint":false},{"year":2005,"finding":"Protein phosphatase 2A (PP2A) dephosphorylates γ-H2AX to resolve DNA damage foci after repair. PP2A catalytic subunit co-immunoprecipitates and co-localizes with γ-H2AX in foci; PP2A dephosphorylates γ-H2AX in vitro; inhibition or RNAi silencing of PP2A causes persistent γ-H2AX foci, inefficient DNA repair, and hypersensitivity to DNA damage.","method":"Co-immunoprecipitation, colocalization, in vitro phosphatase assay, RNAi knockdown, clonogenic survival","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1-2 — in vitro phosphatase assay plus Co-IP plus RNAi with defined phenotype","pmids":["16310392"],"is_preprint":false},{"year":2006,"finding":"H2AX is phosphorylated by JNK activated by UVA, and this phosphorylation is required for DNA ladder formation (internucleosomal DNA fragmentation) during apoptosis but not for caspase-3 activation. H2AX phosphorylation is critical for DNA degradation by caspase-activated DNase (CAD) in vitro.","method":"H2AX-/- mouse embryonic fibroblasts, in vitro CAD assay, JNK kinase assay, caspase activity measurement","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1-2 — in vitro reconstitution plus genetic knockout with specific apoptotic readout","pmids":["16818236"],"is_preprint":false},{"year":2006,"finding":"DNA-PK (not ATM) is solely responsible for H2AX phosphorylation during apoptotic DNA fragmentation; ATM is degraded before DNA fragmentation occurs, while DNA-PKcs is robustly activated (autophosphorylation at S2056) in apoptotic cells before being inactivated by proteolysis.","method":"DNA-PKcs-/- and ATM-/- cells, immunoblotting, kinase activity assays in apoptotic vs. non-apoptotic cells","journal":"DNA repair","confidence":"High","confidence_rationale":"Tier 2 — genetic knockouts with specific apoptotic context, mechanistic dissection of kinase identity","pmids":["16567133"],"is_preprint":false},{"year":2007,"finding":"TIP60 histone acetyltransferase acetylates H2AX following ionizing radiation, and this acetylation is prerequisite for subsequent ubiquitination of H2AX by the TIP60-UBC13 complex. The sequential acetylation and ubiquitination leads to release of H2AX from damaged chromatin, promoting chromatin dynamics required for DNA damage response.","method":"In vivo acetylation and ubiquitination assays, TIP60/UBC13 co-immunoprecipitation, dominant negative and knockdown experiments","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1-2 — identification of writer enzymes with ordered PTM cascade, multiple orthogonal methods","pmids":["17709392"],"is_preprint":false},{"year":2008,"finding":"FACT (Spt16/SSRP1) complex is the major regulator of nucleosomal H2AX exchange; DNA-PK phosphorylation of H2AX facilitates FACT-mediated H2AX exchange by inducing nucleosome conformational changes, while PARP1-mediated poly-ADP-ribosylation of Spt16 inhibits FACT activity for H2AX exchange.","method":"Biochemical purification of H2AX-associated factors, in vitro nucleosome exchange assays, Co-IP, inhibitor treatments","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 — reconstituted in vitro exchange assay with purified components plus mechanistic dissection","pmids":["18406329"],"is_preprint":false},{"year":2008,"finding":"A PP4 phosphatase complex (PP4C/PP4R2/PP4R3β) specifically dephosphorylates ATR-mediated γ-H2AX generated during DNA replication. PP4 directly dephosphorylates γ-H2AX within mononucleosomes in vitro; PP4 silencing causes persistent replication-associated γ-H2AX foci and hypersensitivity to replication inhibitors but not radiomimetic drugs.","method":"In vitro phosphatase assay on mononucleosomes, RNAi knockdown, clonogenic survival with replication inhibitors vs. radiomimetics","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1-2 — in vitro phosphatase assay plus RNAi with context-specific phenotype","pmids":["18614045"],"is_preprint":false},{"year":2009,"finding":"EYA protein tyrosine phosphatase dephosphorylates H2AX at tyrosine 142 (Y142) of the C-terminal tail. Phosphorylation of Y142 determines whether DNA repair factors or pro-apoptotic factors are recruited to γ-H2AX (phospho-S139); dephosphorylation of Y142 by EYA promotes DNA repair and survival over apoptosis.","method":"In vitro phosphatase assay, co-immunoprecipitation, mass spectrometry identification of Y142, genetic epistasis in mammalian cells","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1-2 — identification of novel PTM site with in vitro phosphatase assay and functional consequence on repair vs. apoptosis decision","pmids":["19234442"],"is_preprint":false},{"year":2009,"finding":"miR-24 is upregulated during terminal hematopoietic differentiation and suppresses H2AX expression by targeting conserved binding sites in the H2AX 3'UTR. miR-24-mediated H2AX reduction renders terminally differentiated blood cells hypersensitive to DNA damage; this phenotype is rescued by miR-24-insensitive H2AX.","method":"miRNA target validation (3'UTR reporter assays), Western blot, γ-irradiation sensitivity assays in differentiated vs. undifferentiated cells, rescue with miR-24-resistant H2AX","journal":"Nature structural & molecular biology","confidence":"High","confidence_rationale":"Tier 2 — direct 3'UTR validation plus rescue experiment with miR-24-insensitive H2AX","pmids":["19377482"],"is_preprint":false},{"year":2010,"finding":"Wip1 phosphatase directly dephosphorylates γ-H2AX in vitro and in vivo; ectopic Wip1 expression reduces γ-H2AX after ionizing radiation, disrupts recruitment of DNA repair factors to damage sites, and delays repair. Wip1 deletion enhances γ-H2AX in cells under oncogenic stress.","method":"In vitro phosphatase assay, ectopic Wip1 expression, Wip1 knockout, immunofluorescence for repair factor recruitment","journal":"Cancer research","confidence":"High","confidence_rationale":"Tier 1-2 — in vitro phosphatase assay plus genetic knockout plus overexpression with functional repair readout","pmids":["20460517"],"is_preprint":false},{"year":2010,"finding":"H2AX prevents CtIP-mediated DNA end resection of hairpin-sealed coding ends in G1-phase lymphocytes. In the absence of H2AX, CtIP can open RAG-generated hairpin ends and resect DNA, leading to aberrant NHEJ using micro-homologies and chromosomal deletions. This protective function of H2AX requires γ-H2AX and MDC1.","method":"H2AX-/- mouse lymphocytes, genetic epistasis with CtIP and MDC1, sequencing of V(D)J junctions, cytogenetic analysis","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis in primary lymphocytes with specific molecular and cytogenetic readouts","pmids":["21160476"],"is_preprint":false},{"year":2011,"finding":"Monoubiquitination of H2AX at Lys119/Lys120 mediated by the RNF2-BMI1 E3 ligase complex is required for efficient γ-H2AX formation and DNA damage response signaling. RNF2-BMI1 interacts with H2AX in a DNA damage-dependent manner; H2AX K120R mutation abolishes monoubiquitination, impairs ATM recruitment to DSBs, and reduces MDC1 accumulation.","method":"Co-immunoprecipitation, ubiquitination assay, site-directed mutagenesis (K119R/K120R), siRNA knockdown, immunofluorescence for DSB markers","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — identification of E3 ligase and ubiquitination sites with mutagenesis and functional epistasis","pmids":["21676867"],"is_preprint":false},{"year":2003,"finding":"DNA-PK is activated by nucleosomes through Ku binding to nucleosomal DNA ends, and the activated complex phosphorylates H2AX within the nucleosome context. Histone acetylation greatly enhances DNA-PK-mediated H2AX phosphorylation within nucleosomes but not when H2AX is in free form.","method":"In vitro kinase assays with reconstituted nucleosomes, Ku binding assays, comparison of acetylated vs. non-acetylated nucleosomal substrates","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 1 — reconstituted in vitro kinase assay with purified nucleosomal components","pmids":["14627815"],"is_preprint":false},{"year":2005,"finding":"ATM-dependent phosphorylation of H2AX occurs during mitosis in normally growing (unirradiated) mammalian cells, revealing a DNA damage-independent role for γ-H2AX. Two distinct focal populations of γ-H2AX exist: large amorphous foci recruiting DSB repair proteins and smaller foci that do not recruit repair proteins.","method":"Quantitative in situ immunofluorescence, cell cycle analysis, ATM inhibition in unirradiated cells","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 — direct localization with cell cycle analysis and ATM inhibition, single lab study","pmids":["16030261"],"is_preprint":false},{"year":2008,"finding":"GABA(A) receptor signaling in embryonic stem cells signals through S-phase checkpoint kinases (PIKKs) and histone H2AX to regulate stem cell proliferation, independent of differentiation, apoptosis, or DNA damage; H2AX functions as an effector downstream of GABA(A) receptor-induced hyperpolarization to control S-phase checkpoint-mediated proliferation.","method":"GABA(A) receptor pharmacology, flow cytometry, genetic manipulation of H2AX in ES and neural crest stem cells","journal":"Nature","confidence":"Medium","confidence_rationale":"Tier 2 — pathway placement by pharmacological and genetic approaches, but mechanistic link to H2AX is indirect","pmids":["18515516"],"is_preprint":false},{"year":2009,"finding":"H2AX overexpression activates Nox1-mediated ROS generation through a pathway involving Rac1 GTPase; H2AX reduces the interaction between Nox1 activator NOXA1 and its inhibitor 14-3-3ζ, thereby increasing Nox1 activity and promoting cell death after DNA damage.","method":"H2AX overexpression and knockdown, Nox1 activity assays, Rac1 dominant-negative expression, NAC treatment, Co-IP of NOXA1/14-3-3ζ","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2-3 — Co-IP and functional assays with multiple inhibitors, single lab","pmids":["22237206"],"is_preprint":false},{"year":2008,"finding":"Rvb1 is required for the histone acetyltransferase activity of the Tip60/NuA4 complex; Rvb1 depletion mimics Tip60 depletion in causing persistence of phospho-H2AX after DNA damage. H4 acetylation by Tip60 is required prior to γ-H2AX dephosphorylation, linking the Rvb1-Tip60 complex to γ-H2AX removal.","method":"RNAi knockdown of Rvb1 vs. Ino80 vs. SRCAP vs. Tip60, HAT activity assay, γ-H2AX immunofluorescence","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2 — enzymatic activity assay plus RNAi epistasis, single lab","pmids":["18285460"],"is_preprint":false},{"year":2009,"finding":"H2AX is required for cell cycle arrest via the p53/p21 pathway after replication stalling; absence of H2AX leads to proteasome-dependent p21 degradation followed by caspase-dependent mitotic catastrophe, while H2AX-proficient cells increase p21 and arrest the cell cycle.","method":"H2AX-/- cells, RNAi, adeno-associated virus model of pannuclear γ-H2AX, proteasome inhibitors, p21 immunoblotting","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2 — genetic knockout with pathway analysis, single lab but multiple mechanistic readouts","pmids":["19273588"],"is_preprint":false},{"year":2008,"finding":"ATR and H2AX cooperate to maintain genome stability under replication stress; in ATR-deficient cells, H2AX is phosphorylated by ATM and DNA-PKcs and promotes Rad51 focal accumulation (homologous recombination); dual ATR/H2AX deficiency causes synergistic increases in chromatid breaks and translocations. The S139 phosphorylation site of H2AX is specifically required.","method":"ATR-deficient cells combined with H2AX-/- cells, Rad51 immunofluorescence, cytogenetic analysis, H2AX S139A mutant reconstitution","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis with site-specific mutant, synergistic phenotype in double-deficient cells","pmids":["19049966"],"is_preprint":false},{"year":2012,"finding":"AIF-mediated caspase-independent necroptosis requires γ-H2AX (S139-phosphorylated H2AX); AIF associates with γ-H2AX in the nucleus to form a DNA-degrading complex. ATM and DNA-PK synergistically phosphorylate H2AX at S139 to enable necroptosis; H2AX S139A mutant or H2AX-/- cells are resistant to necroptosis, while phosphomimetic H2AX-S139E restores sensitivity.","method":"H2AX-/- cells, ATM/DNA-PK inhibitors, H2AX S139A and S139E mutant reconstitution, Co-IP of AIF/γ-H2AX","journal":"Cell death & disease","confidence":"High","confidence_rationale":"Tier 2 — phospho-site mutants plus kinase knockouts plus Co-IP establish mechanism","pmids":["22972376"],"is_preprint":false},{"year":2014,"finding":"Dub3 deubiquitinase directly deubiquitinates H2AX; Dub3 overexpression decreases DNA damage-induced H2AX monoubiquitination and abrogates 53BP1 and BRCA1 focus formation (but not MDC1 or γ-H2AX foci), while Dub3 depletion has the opposite effect. Dub3 counteracts the H2AX E3 ligases RNF8 and RNF168.","method":"In vitro deubiquitinase assay, Co-IP of Dub3/H2AX, overexpression of wild-type vs. catalytically inactive Dub3, RNAi, immunofluorescence","journal":"Molecular oncology","confidence":"High","confidence_rationale":"Tier 1-2 — in vitro deubiquitinase assay plus Co-IP plus catalytic mutant controls","pmids":["24704006"],"is_preprint":false},{"year":2019,"finding":"PRMT5 sustains RNF168 expression; suppression of PRMT5 (in MTAP-deficient cells) reduces RNF168 levels, leading to H2AX destabilization by E3 ubiquitin ligase SMURF2. RNF168 and SMURF2 serve as a stabilizer and destabilizer of H2AX respectively through dynamic interactions with H2AX, forming a proteostasis regulatory axis.","method":"Co-immunoprecipitation, RNAi knockdown, protein stability assays, MTAP-deficient glioblastoma cells","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2-3 — Co-IP plus genetic manipulation, single lab","pmids":["31533041"],"is_preprint":false},{"year":2020,"finding":"H2AX glutamate 141 (E141) is ADP-ribosylated following oxidative DNA damage; this modification recruits Neil3 glycosylase to DNA damage sites for base excision repair. Loss of E141 ADP-ribosylation enhances S139 phosphorylation (γH2AX) and erroneously triggers DSB response factors, indicating ADP-ribosylation suppresses the DSB response during BER.","method":"Unbiased mass spectrometry identification of ADP-ribosylation site, H2AX E141A mutant, Neil3 Co-IP, BER functional assays","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1-2 — MS identification of novel PTM site with site-directed mutant and functional assay, multiple orthogonal methods","pmids":["33264433"],"is_preprint":false},{"year":2016,"finding":"Chronic oxidative stress promotes H2AX poly-ubiquitination by RNF168 and subsequent proteasomal degradation; persistent ROS (due to deficient JunD/Nrf2 antioxidant response) enhances H2AX-RNF168 interaction and H2AX turnover, reducing DNA repair capacity.","method":"Co-immunoprecipitation of H2AX-RNF168, ubiquitination assays, proteasome inhibition, ROS modulation, primary TNBC patient samples","journal":"EMBO molecular medicine","confidence":"Medium","confidence_rationale":"Tier 2-3 — Co-IP plus ubiquitination assay plus patient samples, single lab","pmids":["27006338"],"is_preprint":false},{"year":2023,"finding":"SIRT1 deacetylates H2AX at Lys5; acetylation of H2AX at K5 (mimicked by K5Q mutation) impairs Ser139 phosphorylation in response to DNA damage. SIRT1 deficiency in cardiomyocytes elevates K5 acetylation of H2AX and blunts Ser139 phosphorylation, enhancing doxorubicin-induced cardiotoxicity.","method":"Cardiomyocyte-specific Sirt1 knockout mice, H2AX K5Q and S139A mutants, immunostaining for acetyl-K5-H2AX and phospho-S139-H2AX, caspase-3 activation assay","journal":"Cardiovascular research","confidence":"High","confidence_rationale":"Tier 2 — genetic knockout plus site-specific mutants identifying SIRT1 as H2AX K5 deacetylase with functional consequence on S139 phosphorylation","pmids":["35258628"],"is_preprint":false},{"year":2020,"finding":"γH2AX domains spread primarily along chromosomal contacts of a DSB site as determined by topological architecture; DSBs that disrupt a topological border allow γH2AX to extend into both adjacent compartments, while DSBs near a border produce highly asymmetric γH2AX platforms with near-absence from one broken end.","method":"Hi-C/chromatin conformation capture combined with ChIP-seq for γH2AX at defined DSBs","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 — genome-wide structural analysis linking 3D chromosome contacts to γH2AX spreading mechanism","pmids":["32572033"],"is_preprint":false},{"year":2021,"finding":"HMGA2 induces DNA nicks at transcription start sites, which enables the FACT complex to incorporate H2AX-containing nucleosomes; phosphorylation of H2AX at S139 (γH2AX) at these sites is required for repair-mediated active DNA demethylation and transcription activation.","method":"ChIP-seq, HMGA2 knockdown, FACT complex inhibition, H2AX phosphorylation site mutants, bisulfite sequencing for DNA methylation","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 — multiple orthogonal methods but non-canonical H2AX function, single lab","pmids":["33594057"],"is_preprint":false},{"year":2020,"finding":"UBE2T-RNF8 E2-E3 ubiquitin ligase pair monoubiquitinates H2AX/γH2AX at K119/K120 upon radiation; this monoubiquitination facilitates CHK1 phosphorylation and CHK1 release from chromatin for activation. H2AX K119/120R mutation abolishes monoubiquitination and abrogates CHK1 activation.","method":"Co-immunoprecipitation, ubiquitination assays, chromatin fractionation, H2AX K119/120R mutant, CHK1 activation assays, xenograft models","journal":"Journal of experimental & clinical cancer research","confidence":"Medium","confidence_rationale":"Tier 2-3 — Co-IP plus site-directed mutagenesis plus functional CHK1 assay, single lab","pmids":["33087136"],"is_preprint":false},{"year":2015,"finding":"In female mice with chromosome abnormalities (e.g., XO Turner syndrome), asynapsed chromosomes during meiotic prophase I trigger oocyte elimination at diplonema linked to γH2AX presence; deletion or point mutation of H2afx restores oocyte numbers in XO females to wild-type (XX) levels, establishing H2AX phosphorylation as a driver (not merely marker) of oocyte elimination.","method":"H2afx-/- and H2afx point-mutant mice on XO background, immunofluorescence for γH2AX, oocyte counting at diplonema","journal":"PLoS genetics","confidence":"High","confidence_rationale":"Tier 2 — genetic rescue with H2afx null and point mutant, specific cellular phenotype (oocyte loss)","pmids":["26509888"],"is_preprint":false},{"year":2018,"finding":"Histone acetyltransferase MOF regulates the expansion of H2AX phosphorylation (γH2AX) in spermatocytes during all three meiotic waves (leptonema, zygonema, pachynema). Germ cell-specific Mof deletion causes loss of H4K16 acetylation, restricts γH2AX to chromosomal axes without chromatin-wide expansion, and causes MSCI failure and DSB repair defects.","method":"Germ cell-specific Mof knockout (Stra8-Cre), immunofluorescence for γH2AX and MDC1, chromosome spreading, crossover analysis","journal":"PLoS genetics","confidence":"High","confidence_rationale":"Tier 2 — cell-type specific conditional knockout with multiple mechanistic readouts demonstrating MOF as regulator of γH2AX spreading","pmids":["29795555"],"is_preprint":false},{"year":2016,"finding":"γH2AX signaling is a prerequisite for damage-induced chromosome territory relocation; cells deficient in γH2AX signaling fail to relocate chromosome territories after DSBs. γH2AX signaling promotes nuclear myosin 1 (NM1) recruitment to chromatin, and NM1 motor function is essential for chromosome territory movement.","method":"H2AX-deficient cells, immunofluorescence for chromosome territories (FISH), NM1 motor-dead mutants, chromatin fractionation","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2-3 — genetic deficiency with FISH readout and mechanistic follow-up with motor mutants, single lab","pmids":["27365048"],"is_preprint":false}],"current_model":"H2AX is a histone H2A variant that becomes rapidly phosphorylated at serine 139 (forming γ-H2AX) by ATM (primary kinase after DSBs), DNA-PK (redundant with ATM for IR-induced breaks; sole kinase during apoptosis), or ATR (at stalled replication forks and during meiosis), spreading across megabase chromatin domains defined by topological chromosomal contacts to serve as a platform for recruitment of DNA damage response factors (including 53BP1, MDC1, INO80, and BRCA1); γ-H2AX is removed by phosphatases PP2A (after exogenous damage) and PP4 (after replication stress), and its chromatin dynamics are further regulated by sequential TIP60-mediated acetylation and UBC13-mediated ubiquitination that promote H2AX eviction, by FACT-mediated nucleosome exchange stimulated by DNA-PK phosphorylation, by monoubiquitination at K119/K120 by RNF2-BMI1/RNF8 (promoting ATM and CHK1 activation) counteracted by Dub3 deubiquitinase, by Y142 dephosphorylation by EYA phosphatase that shifts the balance from apoptosis to repair, by SIRT1-mediated deacetylation at K5 that enables S139 phosphorylation, and by ADP-ribosylation at E141 that directs base excision repair; H2AX is required for G2-M checkpoint activation, prevention of aberrant DNA end resection in G1 lymphocytes, genomic stability during V(D)J recombination and class switch recombination, meiotic sex chromosome inactivation, and DNA ladder formation during apoptosis, while its expression level is post-transcriptionally controlled by miR-24 and miR-138, and its protein stability is regulated by a PRMT5-RNF168-SMURF2 proteostasis axis."},"narrative":{"teleology":[{"year":1998,"claim":"The discovery that DSBs induce rapid phosphorylation of H2AX at S139 across ~2 Mb chromatin domains established γ-H2AX as a large-scale chromatin mark for broken DNA, raising the question of which kinases are responsible and what downstream effectors are recruited.","evidence":"2D gel electrophoresis and 32P incorporation in irradiated mammalian cells and mice","pmids":["9488723"],"confidence":"High","gaps":["Kinase identity unknown","Functional consequence of modification not yet tested","Whether phosphorylation is strictly DSB-specific was not addressed"]},{"year":2001,"claim":"Identification of ATM as the primary H2AX kinase after DSBs, with DNA-PK providing residual activity, answered the kinase-identity question and established that PIKK family members are the writers of γ-H2AX.","evidence":"In vitro kinase assay, ATM−/− and DNA-PKcs−/− cell lines, rescue by ectopic ATM expression","pmids":["11571274"],"confidence":"High","gaps":["ATR contribution at replication forks not yet tested","Relative contributions of ATM vs. DNA-PK in different damage contexts not resolved"]},{"year":2002,"claim":"Demonstrating that H2AX−/− mice phenocopy ATM−/− cells for G2-M checkpoint failure at low DSB doses established γ-H2AX as a signal amplifier required for threshold-level checkpoint activation, not merely a damage marker.","evidence":"H2AX−/− and 53BP1−/− mouse knockouts, flow cytometry, 53BP1 foci immunofluorescence","pmids":["12447390"],"confidence":"High","gaps":["Whether H2AX contributes to S-phase or G1 checkpoints was unknown","Mechanism of signal amplification not molecularly defined"]},{"year":2003,"claim":"Direct binding of 53BP1 to phosphorylated (but not unphosphorylated) H2AX, combined with evidence that DNA-PK phosphorylates H2AX within nucleosomes enhanced by acetylation, established the first molecular link between γ-H2AX and effector recruitment and defined chromatin context as a regulatory layer.","evidence":"In vitro binding assays with H2AX phospho-mutant reconstitution; reconstituted nucleosomal kinase assays","pmids":["12697768","14627815"],"confidence":"High","gaps":["MDC1 as an intermediary adaptor not yet characterized","Whether 53BP1 binding is direct to γ-H2AX or indirect through other marks was debated"]},{"year":2003,"claim":"Showing that H2AX haploinsufficiency causes genomic instability and that phosphorylation-site mutants (S→A, S→E) fail to rescue H2AX-null phenotypes established H2AX as a dosage-dependent, phosphorylation-dependent tumor suppressor.","evidence":"H2AX+/−, H2AX−/−, p53−/− double-knockout mice with transgenic phospho-site mutant reconstitution and cytogenetics","pmids":["12914701","12914700"],"confidence":"High","gaps":["Specific repair pathway(s) compromised by haploinsufficiency not identified","Whether phosphomimetic failure reflects structural requirements beyond charge not tested"]},{"year":2004,"claim":"ATM and DNA-PK were shown to be redundant for IR-induced γ-H2AX (requiring ablation of both to eliminate signal), while the INO80 chromatin remodeling complex was identified as a γ-H2AX-dependent effector recruited to DSBs, expanding the reader network beyond checkpoint proteins to chromatin remodelers.","evidence":"ATM/DNA-PK double-deficient cells with epistasis analysis; Co-IP and ChIP of INO80 at HO-induced DSBs in yeast","pmids":["15059890","15607974"],"confidence":"High","gaps":["Whether INO80 recruitment via γ-H2AX is conserved in mammals not shown","SWR1/SRCAP remodeler contributions not yet addressed"]},{"year":2004,"claim":"Discovery that ATR phosphorylates H2AX on the XY body in a BRCA1-dependent manner for meiotic sex chromosome inactivation extended γ-H2AX function beyond DNA repair to programmed chromatin silencing during gametogenesis.","evidence":"Immunofluorescence of ATR and γ-H2AX in wild-type vs. BRCA1-mutant spermatocytes","pmids":["15589157"],"confidence":"High","gaps":["How ATR-dependent γ-H2AX recruits silencing machinery was not identified","Whether H2AX phosphorylation is sufficient for MSCI without other marks not tested"]},{"year":2005,"claim":"Identification of PP2A as the phosphatase that dephosphorylates γ-H2AX after repair completion answered how damage foci are resolved and revealed that persistent γ-H2AX impairs repair and cell survival.","evidence":"Co-IP, in vitro phosphatase assay, PP2A RNAi causing persistent γ-H2AX foci and radiosensitivity","pmids":["16310392"],"confidence":"High","gaps":["Whether PP2A acts on nucleosomal γ-H2AX or requires eviction not tested","Context-specificity relative to replication stress not addressed"]},{"year":2006,"claim":"Demonstrating that DNA-PK (not ATM) phosphorylates H2AX during apoptosis, and that JNK-mediated H2AX phosphorylation is required for DNA ladder formation by CAD, established distinct kinase usage in apoptotic versus repair contexts and a pro-death effector role for γ-H2AX.","evidence":"DNA-PKcs−/− and ATM−/− cells in apoptotic conditions; H2AX−/− MEFs with in vitro CAD assay","pmids":["16567133","16818236"],"confidence":"High","gaps":["How γ-H2AX facilitates CAD-mediated cleavage structurally was not defined","Whether this applies to all apoptotic stimuli was not tested"]},{"year":2007,"claim":"Elucidation of a sequential TIP60 acetylation → UBC13 ubiquitination cascade on H2AX that promotes its eviction from damaged chromatin revealed that γ-H2AX removal is an actively regulated process requiring ordered PTMs.","evidence":"In vivo acetylation and ubiquitination assays, TIP60/UBC13 Co-IP, dominant-negative and knockdown experiments","pmids":["17709392"],"confidence":"High","gaps":["Specific acetylation site on H2AX not mapped","Whether eviction is required for repair completion or just foci resolution was unclear"]},{"year":2008,"claim":"Identification of FACT as the H2AX nucleosome exchange factor stimulated by DNA-PK phosphorylation, PP4 as the replication-stress-specific γ-H2AX phosphatase, and Rvb1-TIP60 as the HAT complex required for γ-H2AX removal collectively established that γ-H2AX dynamics are governed by context-specific writer-eraser-remodeler modules.","evidence":"In vitro nucleosome exchange with purified FACT; PP4 phosphatase assay on mononucleosomes with replication-stress specificity; Rvb1 RNAi epistasis with TIP60","pmids":["18406329","18614045","18285460"],"confidence":"High","gaps":["How FACT discriminates H2AX-containing vs. canonical H2A nucleosomes not defined","Whether PP4 and PP2A act on distinct pools simultaneously was not tested"]},{"year":2009,"claim":"Discovery that EYA dephosphorylates H2AX Y142 to switch the γ-H2AX platform from apoptosis to repair, and that miR-24 post-transcriptionally silences H2AX during differentiation, established two new regulatory layers — a PTM-encoded fate switch and a microRNA-based expression control mechanism.","evidence":"In vitro EYA phosphatase assay, mass spectrometry for Y142, genetic epistasis; miR-24 3′UTR reporter with rescue by miR-24-insensitive H2AX","pmids":["19234442","19377482"],"confidence":"High","gaps":["WSTF kinase (Y142 writer) interaction with EYA not mechanistically dissected","Whether miR-24 regulation is conserved beyond hematopoiesis not shown"]},{"year":2010,"claim":"Showing that H2AX prevents CtIP-mediated aberrant end resection at RAG-generated hairpin ends in G1 lymphocytes revealed a cell-cycle- and context-specific protective function of γ-H2AX-MDC1 in enforcing faithful NHEJ during V(D)J recombination.","evidence":"H2AX−/− lymphocytes with CtIP/MDC1 genetic epistasis, V(D)J junction sequencing, cytogenetics","pmids":["21160476"],"confidence":"High","gaps":["Whether this protective mechanism extends to class-switch recombination junctions was not shown","How γ-H2AX physically blocks CtIP access was not defined"]},{"year":2011,"claim":"Identification of RNF2-BMI1 as the E3 ligase for H2AX K119/K120 monoubiquitination, required for ATM recruitment and full γ-H2AX signaling, established ubiquitination as a prerequisite for (not just consequence of) the DSB response.","evidence":"Co-IP, ubiquitination assay, K119R/K120R mutants, siRNA with DSB marker readouts","pmids":["21676867"],"confidence":"High","gaps":["Whether RNF2-BMI1 acts before or after initial S139 phosphorylation was not resolved temporally","Relationship to RNF8/RNF168-mediated ubiquitin signaling not fully distinguished"]},{"year":2012,"claim":"Demonstrating that AIF forms a nuclear DNA-degrading complex with γ-H2AX during necroptosis, dependent on ATM/DNA-PK-mediated S139 phosphorylation, established a role for H2AX in caspase-independent programmed cell death.","evidence":"H2AX−/− cells, kinase inhibitors, S139A/S139E mutant reconstitution, AIF-γ-H2AX Co-IP","pmids":["22972376"],"confidence":"High","gaps":["How AIF recognizes γ-H2AX specifically (binding interface) was not defined","Whether this mechanism operates in vivo during pathological necroptosis not shown"]},{"year":2014,"claim":"Identification of Dub3 as a deubiquitinase that directly removes ubiquitin from H2AX, counteracting RNF8/RNF168, and selectively suppressing 53BP1/BRCA1 foci without affecting MDC1 or γ-H2AX, revealed a deubiquitination-based mechanism for fine-tuning downstream effector recruitment.","evidence":"In vitro DUB assay, catalytically inactive Dub3 mutant, Co-IP, immunofluorescence","pmids":["24704006"],"confidence":"High","gaps":["Whether Dub3 acts on mono- or poly-ubiquitinated H2AX preferentially not determined","Physiological context regulating Dub3 activity at DSBs unknown"]},{"year":2015,"claim":"Genetic rescue of oocyte loss in XO mice by H2AX deletion or point mutation established γ-H2AX as a functional driver of oocyte elimination triggered by asynapsed chromosomes, extending H2AX function to meiotic quality control in females.","evidence":"H2AX−/− and point-mutant mice on XO background, oocyte counting, γ-H2AX immunofluorescence","pmids":["26509888"],"confidence":"High","gaps":["Downstream effectors linking γ-H2AX to oocyte apoptosis not identified","Whether this mechanism applies to autosomal asynapsis was not tested"]},{"year":2016,"claim":"Chronic oxidative stress was shown to promote RNF168-mediated poly-ubiquitination and proteasomal degradation of H2AX, while γ-H2AX signaling was found to drive chromosome territory relocation via nuclear myosin 1, revealing proteostatic vulnerability and a mechanical effector function of γ-H2AX.","evidence":"ROS modulation with RNF168 Co-IP and ubiquitination assays; H2AX-deficient cells with FISH and NM1 motor-dead mutants","pmids":["27006338","27365048"],"confidence":"Medium","gaps":["Whether RNF168-dependent H2AX degradation is a general stress response or tumor-specific is unclear","How γ-H2AX recruits NM1 mechanistically is not defined","Single-lab findings for chromosome territory relocation"]},{"year":2018,"claim":"Conditional MOF deletion in spermatocytes demonstrated that H4K16 acetylation by MOF is required for chromatin-wide γ-H2AX spreading during all three meiotic waves, distinguishing axis-restricted from chromatin-wide γ-H2AX as functionally distinct states.","evidence":"Germ cell-specific Mof knockout, chromosome spreading, γ-H2AX and MDC1 immunofluorescence","pmids":["29795555"],"confidence":"High","gaps":["Whether MOF acts by enabling ATR/ATM access or by facilitating MDC1 spreading not distinguished","Applicability to somatic DSB-induced γ-H2AX spreading not tested"]},{"year":2019,"claim":"The PRMT5–RNF168–SMURF2 axis was identified as a proteostasis circuit controlling H2AX protein levels, where PRMT5 sustains RNF168 to stabilize H2AX while SMURF2 promotes its degradation, linking epigenetic enzyme activity to H2AX abundance.","evidence":"Co-IP, RNAi, protein stability assays in MTAP-deficient glioblastoma cells","pmids":["31533041"],"confidence":"Medium","gaps":["Whether SMURF2-mediated degradation is ubiquitin-dependent at the same sites as RNF168 mono-ub was not clarified","Single-lab study in a specific genetic context (MTAP-deleted)","In vivo validation lacking"]},{"year":2020,"claim":"Hi-C-resolved mapping of γ-H2AX domains showed that spreading follows pre-existing 3D chromosomal contacts rather than linear distance, while ADP-ribosylation at E141 was discovered to direct BER and suppress erroneous DSB signaling, together refining the spatial and PTM logic of H2AX-based damage signaling.","evidence":"Hi-C + ChIP-seq at defined DSBs; mass spectrometry identification of E141 ADP-ribosylation with site mutant and Neil3 Co-IP","pmids":["32572033","33264433"],"confidence":"High","gaps":["Whether cohesin or condensin mediate the contact-dependent spreading was not tested","Which ADP-ribosyltransferase modifies E141 was not identified"]},{"year":2023,"claim":"SIRT1 was identified as the deacetylase for H2AX K5, and K5 acetylation was shown to impair S139 phosphorylation, establishing a crosstalk in which acetylation state gates the canonical γ-H2AX response.","evidence":"Cardiomyocyte-specific Sirt1 knockout, H2AX K5Q and S139A mutants, acetyl-K5 and phospho-S139 immunostaining","pmids":["35258628"],"confidence":"High","gaps":["The acetyltransferase that writes K5 acetylation was not identified","Whether K5 acetylation inhibits kinase access or promotes phosphatase activity not distinguished"]},{"year":null,"claim":"Key unresolved questions include: the structural basis for how γ-H2AX recruits each specific effector (53BP1, MDC1, AIF); how the multiple PTMs on H2AX (S139-P, Y142-P, K5-Ac, K119/120-Ub, E141-ADP-ribose) are coordinated temporally and spatially in a single nucleosome; and whether the non-canonical roles of H2AX in stem cell proliferation and DNA demethylation represent generalizable mechanisms or context-restricted phenomena.","evidence":"","pmids":[],"confidence":"Low","gaps":["No cryo-EM or crystal structure of γ-H2AX nucleosome with bound effector","Combinatorial PTM code on single H2AX molecules not resolved","In vivo relevance of GABA receptor–H2AX axis and HMGA2–FACT–H2AX demethylation pathway requires independent replication"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0042393","term_label":"histone binding","supporting_discovery_ids":[0,11,19,31]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[0,5,12]}],"localization":[{"term_id":"GO:0005694","term_label":"chromosome","supporting_discovery_ids":[0,6,7,32,36]},{"term_id":"GO:0000228","term_label":"nuclear chromosome","supporting_discovery_ids":[7,35,36]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[0,26,33]}],"pathway":[{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[0,1,2,3,5,6,8,13,14,25,29]},{"term_id":"R-HSA-4839726","term_label":"Chromatin organization","supporting_discovery_ids":[0,6,11,12,19,32,36]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[3,24,25]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[9,10,26]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[17]},{"term_id":"R-HSA-1474165","term_label":"Reproduction","supporting_discovery_ids":[7,35,36]}],"complexes":["nucleosome"],"partners":["ATM","DNA-PKCS","ATR","MDC1","TP53BP1","TIP60","RNF168","SMURF2"],"other_free_text":[]},"mechanistic_narrative":"H2AX is a histone H2A variant that serves as the central chromatin-based platform for the DNA damage response, undergoing rapid phosphorylation at serine 139 (forming γ-H2AX) by ATM, DNA-PK, or ATR kinases across megabase-scale chromatin domains shaped by three-dimensional chromosomal topology, thereby recruiting repair and signaling factors including 53BP1, MDC1, INO80, and BRCA1 [PMID:9488723, PMID:11571274, PMID:12697768, PMID:15607974, PMID:32572033]. γ-H2AX is resolved by context-specific phosphatases — PP2A after exogenous DSBs, PP4 after replication stress, and Wip1 as a general attenuator — while additional post-translational modifications including TIP60-mediated acetylation followed by UBC13-dependent ubiquitination, RNF2-BMI1/RNF8-mediated monoubiquitination at K119/K120, SIRT1-regulated K5 deacetylation, EYA-mediated Y142 dephosphorylation, and E141 ADP-ribosylation collectively tune the balance between DNA repair, checkpoint activation, and apoptosis [PMID:16310392, PMID:18614045, PMID:20460517, PMID:17709392, PMID:21676867, PMID:19234442, PMID:33264433, PMID:35258628]. Beyond canonical DSB repair, H2AX phosphorylation is required for G2-M checkpoint enforcement, prevention of aberrant CtIP-mediated end resection during V(D)J recombination, meiotic sex chromosome inactivation, oocyte quality surveillance, and DNA ladder formation during apoptosis and necroptosis [PMID:12447390, PMID:21160476, PMID:15589157, PMID:26509888, PMID:16818236, PMID:22972376]. H2AX protein levels are post-transcriptionally controlled by miR-24 during hematopoietic differentiation and by a PRMT5–RNF168–SMURF2 proteostasis axis [PMID:19377482, PMID:31533041]."},"prefetch_data":{"uniprot":{"accession":"P16104","full_name":"Histone H2AX","aliases":["Histone H2A.X"],"length_aa":143,"mass_kda":15.1,"function":"Variant histone H2A which replaces conventional H2A in a subset of nucleosomes. Nucleosomes wrap and compact DNA into chromatin, limiting DNA accessibility to the cellular machineries which require DNA as a template. Histones thereby play a central role in transcription regulation, DNA repair, DNA replication and chromosomal stability. DNA accessibility is regulated via a complex set of post-translational modifications of histones, also called histone code, and nucleosome remodeling. Required for checkpoint-mediated arrest of cell cycle progression in response to low doses of ionizing radiation and for efficient repair of DNA double strand breaks (DSBs) specifically when modified by C-terminal phosphorylation","subcellular_location":"Nucleus; Chromosome","url":"https://www.uniprot.org/uniprotkb/P16104/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/H2AX","classification":"Common Essential","n_dependent_lines":861,"n_total_lines":1208,"dependency_fraction":0.7127483443708609},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"NUMA1","stoichiometry":4.0}],"url":"https://opencell.sf.czbiohub.org/search/H2AX","total_profiled":1310},"omim":[{"mim_id":"621534","title":"FAMILY WITH SEQUENCE SIMILARITY 135, MEMBER B; FAM135B","url":"https://www.omim.org/entry/621534"},{"mim_id":"621001","title":"SPERMATOGENIC FAILURE 96; SPGF96","url":"https://www.omim.org/entry/621001"},{"mim_id":"620903","title":"POLYCYSTIC KIDNEY DISEASE 8; PKD8","url":"https://www.omim.org/entry/620903"},{"mim_id":"620686","title":"PREMATURE OVARIAN FAILURE 23; POF23","url":"https://www.omim.org/entry/620686"},{"mim_id":"620610","title":"OOCYTE/ZYGOTE/EMBRYO MATURATION ARREST 21; OZEMA21","url":"https://www.omim.org/entry/620610"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoplasm","reliability":"Supported"},{"location":"Nuclear speckles","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/H2AX"},"hgnc":{"alias_symbol":[],"prev_symbol":["H2AFX"]},"alphafold":{"accession":"P16104","domains":[{"cath_id":"1.10.20.10","chopping":"17-112","consensus_level":"medium","plddt":98.2774,"start":17,"end":112}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P16104","model_url":"https://alphafold.ebi.ac.uk/files/AF-P16104-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P16104-F1-predicted_aligned_error_v6.png","plddt_mean":86.31},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=H2AX","jax_strain_url":"https://www.jax.org/strain/search?query=H2AX"},"sequence":{"accession":"P16104","fasta_url":"https://rest.uniprot.org/uniprotkb/P16104.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P16104/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P16104"}},"corpus_meta":[{"pmid":"9488723","id":"PMC_9488723","title":"DNA double-stranded breaks induce 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gamma-H2AX interaction links ATP-dependent chromatin remodeling to DNA damage repair.","date":"2004","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/15607974","citation_count":448,"is_preprint":false},{"pmid":"19234442","id":"PMC_19234442","title":"Tyrosine dephosphorylation of H2AX modulates apoptosis and survival decisions.","date":"2009","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/19234442","citation_count":438,"is_preprint":false},{"pmid":"12914700","id":"PMC_12914700","title":"Histone H2AX: a dosage-dependent suppressor of oncogenic translocations and tumors.","date":"2003","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/12914700","citation_count":404,"is_preprint":false},{"pmid":"12897845","id":"PMC_12897845","title":"Characteristics of gamma-H2AX foci at DNA double-strand breaks sites.","date":"2003","source":"Biochemistry and cell biology = Biochimie et biologie 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incorporation, in vivo phosphorylation assays in irradiated mammalian cells and mice\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — original discovery with multiple orthogonal biochemical methods, foundational paper with 4387 citations\",\n      \"pmids\": [\"9488723\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"ATM is the major kinase responsible for H2AX phosphorylation at serine 139 in response to DSBs; ATM phosphorylates H2AX in vitro, H2AX phosphorylation is severely compromised in ATM-/- cells, and ectopic ATM expression in ATM-/- cells restores H2AX phosphorylation. DNA-PK accounts for residual phosphorylation in the absence of ATM.\",\n      \"method\": \"In vitro kinase assay, ATM-/- and DNA-PKcs-/- cell lines, rescue by ectopic ATM expression, wortmannin inhibition\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro kinase assay plus genetic knockouts plus rescue experiment, replicated across labs\",\n      \"pmids\": [\"11571274\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"ATM and DNA-PK function redundantly to phosphorylate H2AX after ionizing radiation; ablation of both kinases is required to eliminate IR-induced H2AX phosphorylation. ATR is not involved in H2AX phosphorylation in non-replicating cells. DNA-PK-mediated H2AX phosphorylation contributes to recruitment of MDC1 and 53BP1 to DSB sites.\",\n      \"method\": \"ATM-deficient cells treated with LY294002 (DNA-PK inhibitor); ATM/DNA-PK double-deficient chicken cells; epistasis analysis\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis with pharmacological inhibition, replicated in multiple cell systems\",\n      \"pmids\": [\"15059890\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"H2AX is required for efficient G2-M checkpoint activation after low doses of ionizing radiation; H2AX-/- mice show a G2-M checkpoint defect comparable to ATM-/- cells. H2AX regulates the efficient accumulation of 53BP1 into IR-induced foci, thereby amplifying the damage signal at threshold DSB levels.\",\n      \"method\": \"H2AX-/- and 53BP1-/- mouse genetic knockouts, flow cytometry cell cycle analysis, immunofluorescence for 53BP1 foci\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean genetic knockout with specific cellular phenotype, multiple readouts\",\n      \"pmids\": [\"12447390\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"53BP1 directly binds phosphorylated H2AX (but not unphosphorylated H2AX) through a region upstream of its C-terminus; H2AX phosphorylation at serine 139/140 is required for efficient 53BP1 foci formation at DNA breaks. Hyperphosphorylation and relocalization of 53BP1 occur independently.\",\n      \"method\": \"In vitro binding assays, H2AX-deficient cells reconstituted with wild-type or phosphorylation-deficient H2AX mutants, immunofluorescence\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — in vitro binding assay plus genetic reconstitution with phosphorylation mutants\",\n      \"pmids\": [\"12697768\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"H2AX functions as a dosage-dependent suppressor of genomic instability and tumors; H2AX haploinsufficiency causes genomic instability in normal cells. Restoration of H2AX null allele with wild-type H2AX restores genomic stability and radiation resistance, but substitution of the conserved serine phosphorylation sites (S→A or S→E) abolishes this rescue, demonstrating phosphorylation-dependence.\",\n      \"method\": \"Gene targeting (H2AX-/- and H2AX+/- mice), p53-/- double knockouts, transgenic reconstitution with phosphorylation-site mutants, cytogenetic analysis\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic knockouts with site-specific mutant rescue, replicated independently in two concurrent Cell papers\",\n      \"pmids\": [\"12914701\", \"12914700\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"The INO80 chromatin remodeling complex is recruited to DSBs through a direct interaction with γ-H2AX (phosphorylated H2AX); this interaction requires the Nhp10 HMG-like subunit of INO80. Loss of Nhp10 or γ-H2AX reduces INO80 recruitment to DSBs, linking ATP-dependent chromatin remodeling to DNA repair.\",\n      \"method\": \"Co-immunoprecipitation, chromatin immunoprecipitation at HO endonuclease-induced DSB in yeast, genetic epistasis with RAD52 pathway\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP, ChIP, genetic epistasis in yeast ortholog system\",\n      \"pmids\": [\"15607974\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"BRCA1 is required for recruiting ATR kinase to XY chromatin at the onset of meiotic sex chromosome inactivation (MSCI); ATR then phosphorylates H2AX within the XY body, triggering chromatin condensation and transcriptional repression of sex chromosomes.\",\n      \"method\": \"Immunofluorescence localization of ATR in wild-type vs. BRCA1-mutant pachytene spermatocytes, correlation of ATR localization with H2AX phosphorylation and MSCI\",\n      \"journal\": \"Current biology : CB\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct localization experiment with functional consequence in genetic mutant background\",\n      \"pmids\": [\"15589157\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Protein phosphatase 2A (PP2A) dephosphorylates γ-H2AX to resolve DNA damage foci after repair. PP2A catalytic subunit co-immunoprecipitates and co-localizes with γ-H2AX in foci; PP2A dephosphorylates γ-H2AX in vitro; inhibition or RNAi silencing of PP2A causes persistent γ-H2AX foci, inefficient DNA repair, and hypersensitivity to DNA damage.\",\n      \"method\": \"Co-immunoprecipitation, colocalization, in vitro phosphatase assay, RNAi knockdown, clonogenic survival\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — in vitro phosphatase assay plus Co-IP plus RNAi with defined phenotype\",\n      \"pmids\": [\"16310392\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"H2AX is phosphorylated by JNK activated by UVA, and this phosphorylation is required for DNA ladder formation (internucleosomal DNA fragmentation) during apoptosis but not for caspase-3 activation. H2AX phosphorylation is critical for DNA degradation by caspase-activated DNase (CAD) in vitro.\",\n      \"method\": \"H2AX-/- mouse embryonic fibroblasts, in vitro CAD assay, JNK kinase assay, caspase activity measurement\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — in vitro reconstitution plus genetic knockout with specific apoptotic readout\",\n      \"pmids\": [\"16818236\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"DNA-PK (not ATM) is solely responsible for H2AX phosphorylation during apoptotic DNA fragmentation; ATM is degraded before DNA fragmentation occurs, while DNA-PKcs is robustly activated (autophosphorylation at S2056) in apoptotic cells before being inactivated by proteolysis.\",\n      \"method\": \"DNA-PKcs-/- and ATM-/- cells, immunoblotting, kinase activity assays in apoptotic vs. non-apoptotic cells\",\n      \"journal\": \"DNA repair\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic knockouts with specific apoptotic context, mechanistic dissection of kinase identity\",\n      \"pmids\": [\"16567133\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"TIP60 histone acetyltransferase acetylates H2AX following ionizing radiation, and this acetylation is prerequisite for subsequent ubiquitination of H2AX by the TIP60-UBC13 complex. The sequential acetylation and ubiquitination leads to release of H2AX from damaged chromatin, promoting chromatin dynamics required for DNA damage response.\",\n      \"method\": \"In vivo acetylation and ubiquitination assays, TIP60/UBC13 co-immunoprecipitation, dominant negative and knockdown experiments\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — identification of writer enzymes with ordered PTM cascade, multiple orthogonal methods\",\n      \"pmids\": [\"17709392\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"FACT (Spt16/SSRP1) complex is the major regulator of nucleosomal H2AX exchange; DNA-PK phosphorylation of H2AX facilitates FACT-mediated H2AX exchange by inducing nucleosome conformational changes, while PARP1-mediated poly-ADP-ribosylation of Spt16 inhibits FACT activity for H2AX exchange.\",\n      \"method\": \"Biochemical purification of H2AX-associated factors, in vitro nucleosome exchange assays, Co-IP, inhibitor treatments\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted in vitro exchange assay with purified components plus mechanistic dissection\",\n      \"pmids\": [\"18406329\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"A PP4 phosphatase complex (PP4C/PP4R2/PP4R3β) specifically dephosphorylates ATR-mediated γ-H2AX generated during DNA replication. PP4 directly dephosphorylates γ-H2AX within mononucleosomes in vitro; PP4 silencing causes persistent replication-associated γ-H2AX foci and hypersensitivity to replication inhibitors but not radiomimetic drugs.\",\n      \"method\": \"In vitro phosphatase assay on mononucleosomes, RNAi knockdown, clonogenic survival with replication inhibitors vs. radiomimetics\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — in vitro phosphatase assay plus RNAi with context-specific phenotype\",\n      \"pmids\": [\"18614045\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"EYA protein tyrosine phosphatase dephosphorylates H2AX at tyrosine 142 (Y142) of the C-terminal tail. Phosphorylation of Y142 determines whether DNA repair factors or pro-apoptotic factors are recruited to γ-H2AX (phospho-S139); dephosphorylation of Y142 by EYA promotes DNA repair and survival over apoptosis.\",\n      \"method\": \"In vitro phosphatase assay, co-immunoprecipitation, mass spectrometry identification of Y142, genetic epistasis in mammalian cells\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — identification of novel PTM site with in vitro phosphatase assay and functional consequence on repair vs. apoptosis decision\",\n      \"pmids\": [\"19234442\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"miR-24 is upregulated during terminal hematopoietic differentiation and suppresses H2AX expression by targeting conserved binding sites in the H2AX 3'UTR. miR-24-mediated H2AX reduction renders terminally differentiated blood cells hypersensitive to DNA damage; this phenotype is rescued by miR-24-insensitive H2AX.\",\n      \"method\": \"miRNA target validation (3'UTR reporter assays), Western blot, γ-irradiation sensitivity assays in differentiated vs. undifferentiated cells, rescue with miR-24-resistant H2AX\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct 3'UTR validation plus rescue experiment with miR-24-insensitive H2AX\",\n      \"pmids\": [\"19377482\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Wip1 phosphatase directly dephosphorylates γ-H2AX in vitro and in vivo; ectopic Wip1 expression reduces γ-H2AX after ionizing radiation, disrupts recruitment of DNA repair factors to damage sites, and delays repair. Wip1 deletion enhances γ-H2AX in cells under oncogenic stress.\",\n      \"method\": \"In vitro phosphatase assay, ectopic Wip1 expression, Wip1 knockout, immunofluorescence for repair factor recruitment\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — in vitro phosphatase assay plus genetic knockout plus overexpression with functional repair readout\",\n      \"pmids\": [\"20460517\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"H2AX prevents CtIP-mediated DNA end resection of hairpin-sealed coding ends in G1-phase lymphocytes. In the absence of H2AX, CtIP can open RAG-generated hairpin ends and resect DNA, leading to aberrant NHEJ using micro-homologies and chromosomal deletions. This protective function of H2AX requires γ-H2AX and MDC1.\",\n      \"method\": \"H2AX-/- mouse lymphocytes, genetic epistasis with CtIP and MDC1, sequencing of V(D)J junctions, cytogenetic analysis\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis in primary lymphocytes with specific molecular and cytogenetic readouts\",\n      \"pmids\": [\"21160476\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Monoubiquitination of H2AX at Lys119/Lys120 mediated by the RNF2-BMI1 E3 ligase complex is required for efficient γ-H2AX formation and DNA damage response signaling. RNF2-BMI1 interacts with H2AX in a DNA damage-dependent manner; H2AX K120R mutation abolishes monoubiquitination, impairs ATM recruitment to DSBs, and reduces MDC1 accumulation.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, site-directed mutagenesis (K119R/K120R), siRNA knockdown, immunofluorescence for DSB markers\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — identification of E3 ligase and ubiquitination sites with mutagenesis and functional epistasis\",\n      \"pmids\": [\"21676867\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"DNA-PK is activated by nucleosomes through Ku binding to nucleosomal DNA ends, and the activated complex phosphorylates H2AX within the nucleosome context. Histone acetylation greatly enhances DNA-PK-mediated H2AX phosphorylation within nucleosomes but not when H2AX is in free form.\",\n      \"method\": \"In vitro kinase assays with reconstituted nucleosomes, Ku binding assays, comparison of acetylated vs. non-acetylated nucleosomal substrates\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted in vitro kinase assay with purified nucleosomal components\",\n      \"pmids\": [\"14627815\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"ATM-dependent phosphorylation of H2AX occurs during mitosis in normally growing (unirradiated) mammalian cells, revealing a DNA damage-independent role for γ-H2AX. Two distinct focal populations of γ-H2AX exist: large amorphous foci recruiting DSB repair proteins and smaller foci that do not recruit repair proteins.\",\n      \"method\": \"Quantitative in situ immunofluorescence, cell cycle analysis, ATM inhibition in unirradiated cells\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct localization with cell cycle analysis and ATM inhibition, single lab study\",\n      \"pmids\": [\"16030261\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"GABA(A) receptor signaling in embryonic stem cells signals through S-phase checkpoint kinases (PIKKs) and histone H2AX to regulate stem cell proliferation, independent of differentiation, apoptosis, or DNA damage; H2AX functions as an effector downstream of GABA(A) receptor-induced hyperpolarization to control S-phase checkpoint-mediated proliferation.\",\n      \"method\": \"GABA(A) receptor pharmacology, flow cytometry, genetic manipulation of H2AX in ES and neural crest stem cells\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — pathway placement by pharmacological and genetic approaches, but mechanistic link to H2AX is indirect\",\n      \"pmids\": [\"18515516\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"H2AX overexpression activates Nox1-mediated ROS generation through a pathway involving Rac1 GTPase; H2AX reduces the interaction between Nox1 activator NOXA1 and its inhibitor 14-3-3ζ, thereby increasing Nox1 activity and promoting cell death after DNA damage.\",\n      \"method\": \"H2AX overexpression and knockdown, Nox1 activity assays, Rac1 dominant-negative expression, NAC treatment, Co-IP of NOXA1/14-3-3ζ\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — Co-IP and functional assays with multiple inhibitors, single lab\",\n      \"pmids\": [\"22237206\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Rvb1 is required for the histone acetyltransferase activity of the Tip60/NuA4 complex; Rvb1 depletion mimics Tip60 depletion in causing persistence of phospho-H2AX after DNA damage. H4 acetylation by Tip60 is required prior to γ-H2AX dephosphorylation, linking the Rvb1-Tip60 complex to γ-H2AX removal.\",\n      \"method\": \"RNAi knockdown of Rvb1 vs. Ino80 vs. SRCAP vs. Tip60, HAT activity assay, γ-H2AX immunofluorescence\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — enzymatic activity assay plus RNAi epistasis, single lab\",\n      \"pmids\": [\"18285460\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"H2AX is required for cell cycle arrest via the p53/p21 pathway after replication stalling; absence of H2AX leads to proteasome-dependent p21 degradation followed by caspase-dependent mitotic catastrophe, while H2AX-proficient cells increase p21 and arrest the cell cycle.\",\n      \"method\": \"H2AX-/- cells, RNAi, adeno-associated virus model of pannuclear γ-H2AX, proteasome inhibitors, p21 immunoblotting\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic knockout with pathway analysis, single lab but multiple mechanistic readouts\",\n      \"pmids\": [\"19273588\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"ATR and H2AX cooperate to maintain genome stability under replication stress; in ATR-deficient cells, H2AX is phosphorylated by ATM and DNA-PKcs and promotes Rad51 focal accumulation (homologous recombination); dual ATR/H2AX deficiency causes synergistic increases in chromatid breaks and translocations. The S139 phosphorylation site of H2AX is specifically required.\",\n      \"method\": \"ATR-deficient cells combined with H2AX-/- cells, Rad51 immunofluorescence, cytogenetic analysis, H2AX S139A mutant reconstitution\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis with site-specific mutant, synergistic phenotype in double-deficient cells\",\n      \"pmids\": [\"19049966\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"AIF-mediated caspase-independent necroptosis requires γ-H2AX (S139-phosphorylated H2AX); AIF associates with γ-H2AX in the nucleus to form a DNA-degrading complex. ATM and DNA-PK synergistically phosphorylate H2AX at S139 to enable necroptosis; H2AX S139A mutant or H2AX-/- cells are resistant to necroptosis, while phosphomimetic H2AX-S139E restores sensitivity.\",\n      \"method\": \"H2AX-/- cells, ATM/DNA-PK inhibitors, H2AX S139A and S139E mutant reconstitution, Co-IP of AIF/γ-H2AX\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — phospho-site mutants plus kinase knockouts plus Co-IP establish mechanism\",\n      \"pmids\": [\"22972376\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Dub3 deubiquitinase directly deubiquitinates H2AX; Dub3 overexpression decreases DNA damage-induced H2AX monoubiquitination and abrogates 53BP1 and BRCA1 focus formation (but not MDC1 or γ-H2AX foci), while Dub3 depletion has the opposite effect. Dub3 counteracts the H2AX E3 ligases RNF8 and RNF168.\",\n      \"method\": \"In vitro deubiquitinase assay, Co-IP of Dub3/H2AX, overexpression of wild-type vs. catalytically inactive Dub3, RNAi, immunofluorescence\",\n      \"journal\": \"Molecular oncology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — in vitro deubiquitinase assay plus Co-IP plus catalytic mutant controls\",\n      \"pmids\": [\"24704006\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"PRMT5 sustains RNF168 expression; suppression of PRMT5 (in MTAP-deficient cells) reduces RNF168 levels, leading to H2AX destabilization by E3 ubiquitin ligase SMURF2. RNF168 and SMURF2 serve as a stabilizer and destabilizer of H2AX respectively through dynamic interactions with H2AX, forming a proteostasis regulatory axis.\",\n      \"method\": \"Co-immunoprecipitation, RNAi knockdown, protein stability assays, MTAP-deficient glioblastoma cells\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — Co-IP plus genetic manipulation, single lab\",\n      \"pmids\": [\"31533041\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"H2AX glutamate 141 (E141) is ADP-ribosylated following oxidative DNA damage; this modification recruits Neil3 glycosylase to DNA damage sites for base excision repair. Loss of E141 ADP-ribosylation enhances S139 phosphorylation (γH2AX) and erroneously triggers DSB response factors, indicating ADP-ribosylation suppresses the DSB response during BER.\",\n      \"method\": \"Unbiased mass spectrometry identification of ADP-ribosylation site, H2AX E141A mutant, Neil3 Co-IP, BER functional assays\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — MS identification of novel PTM site with site-directed mutant and functional assay, multiple orthogonal methods\",\n      \"pmids\": [\"33264433\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Chronic oxidative stress promotes H2AX poly-ubiquitination by RNF168 and subsequent proteasomal degradation; persistent ROS (due to deficient JunD/Nrf2 antioxidant response) enhances H2AX-RNF168 interaction and H2AX turnover, reducing DNA repair capacity.\",\n      \"method\": \"Co-immunoprecipitation of H2AX-RNF168, ubiquitination assays, proteasome inhibition, ROS modulation, primary TNBC patient samples\",\n      \"journal\": \"EMBO molecular medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — Co-IP plus ubiquitination assay plus patient samples, single lab\",\n      \"pmids\": [\"27006338\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"SIRT1 deacetylates H2AX at Lys5; acetylation of H2AX at K5 (mimicked by K5Q mutation) impairs Ser139 phosphorylation in response to DNA damage. SIRT1 deficiency in cardiomyocytes elevates K5 acetylation of H2AX and blunts Ser139 phosphorylation, enhancing doxorubicin-induced cardiotoxicity.\",\n      \"method\": \"Cardiomyocyte-specific Sirt1 knockout mice, H2AX K5Q and S139A mutants, immunostaining for acetyl-K5-H2AX and phospho-S139-H2AX, caspase-3 activation assay\",\n      \"journal\": \"Cardiovascular research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic knockout plus site-specific mutants identifying SIRT1 as H2AX K5 deacetylase with functional consequence on S139 phosphorylation\",\n      \"pmids\": [\"35258628\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"γH2AX domains spread primarily along chromosomal contacts of a DSB site as determined by topological architecture; DSBs that disrupt a topological border allow γH2AX to extend into both adjacent compartments, while DSBs near a border produce highly asymmetric γH2AX platforms with near-absence from one broken end.\",\n      \"method\": \"Hi-C/chromatin conformation capture combined with ChIP-seq for γH2AX at defined DSBs\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genome-wide structural analysis linking 3D chromosome contacts to γH2AX spreading mechanism\",\n      \"pmids\": [\"32572033\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"HMGA2 induces DNA nicks at transcription start sites, which enables the FACT complex to incorporate H2AX-containing nucleosomes; phosphorylation of H2AX at S139 (γH2AX) at these sites is required for repair-mediated active DNA demethylation and transcription activation.\",\n      \"method\": \"ChIP-seq, HMGA2 knockdown, FACT complex inhibition, H2AX phosphorylation site mutants, bisulfite sequencing for DNA methylation\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods but non-canonical H2AX function, single lab\",\n      \"pmids\": [\"33594057\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"UBE2T-RNF8 E2-E3 ubiquitin ligase pair monoubiquitinates H2AX/γH2AX at K119/K120 upon radiation; this monoubiquitination facilitates CHK1 phosphorylation and CHK1 release from chromatin for activation. H2AX K119/120R mutation abolishes monoubiquitination and abrogates CHK1 activation.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assays, chromatin fractionation, H2AX K119/120R mutant, CHK1 activation assays, xenograft models\",\n      \"journal\": \"Journal of experimental & clinical cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — Co-IP plus site-directed mutagenesis plus functional CHK1 assay, single lab\",\n      \"pmids\": [\"33087136\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"In female mice with chromosome abnormalities (e.g., XO Turner syndrome), asynapsed chromosomes during meiotic prophase I trigger oocyte elimination at diplonema linked to γH2AX presence; deletion or point mutation of H2afx restores oocyte numbers in XO females to wild-type (XX) levels, establishing H2AX phosphorylation as a driver (not merely marker) of oocyte elimination.\",\n      \"method\": \"H2afx-/- and H2afx point-mutant mice on XO background, immunofluorescence for γH2AX, oocyte counting at diplonema\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic rescue with H2afx null and point mutant, specific cellular phenotype (oocyte loss)\",\n      \"pmids\": [\"26509888\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Histone acetyltransferase MOF regulates the expansion of H2AX phosphorylation (γH2AX) in spermatocytes during all three meiotic waves (leptonema, zygonema, pachynema). Germ cell-specific Mof deletion causes loss of H4K16 acetylation, restricts γH2AX to chromosomal axes without chromatin-wide expansion, and causes MSCI failure and DSB repair defects.\",\n      \"method\": \"Germ cell-specific Mof knockout (Stra8-Cre), immunofluorescence for γH2AX and MDC1, chromosome spreading, crossover analysis\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — cell-type specific conditional knockout with multiple mechanistic readouts demonstrating MOF as regulator of γH2AX spreading\",\n      \"pmids\": [\"29795555\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"γH2AX signaling is a prerequisite for damage-induced chromosome territory relocation; cells deficient in γH2AX signaling fail to relocate chromosome territories after DSBs. γH2AX signaling promotes nuclear myosin 1 (NM1) recruitment to chromatin, and NM1 motor function is essential for chromosome territory movement.\",\n      \"method\": \"H2AX-deficient cells, immunofluorescence for chromosome territories (FISH), NM1 motor-dead mutants, chromatin fractionation\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — genetic deficiency with FISH readout and mechanistic follow-up with motor mutants, single lab\",\n      \"pmids\": [\"27365048\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"H2AX is a histone H2A variant that becomes rapidly phosphorylated at serine 139 (forming γ-H2AX) by ATM (primary kinase after DSBs), DNA-PK (redundant with ATM for IR-induced breaks; sole kinase during apoptosis), or ATR (at stalled replication forks and during meiosis), spreading across megabase chromatin domains defined by topological chromosomal contacts to serve as a platform for recruitment of DNA damage response factors (including 53BP1, MDC1, INO80, and BRCA1); γ-H2AX is removed by phosphatases PP2A (after exogenous damage) and PP4 (after replication stress), and its chromatin dynamics are further regulated by sequential TIP60-mediated acetylation and UBC13-mediated ubiquitination that promote H2AX eviction, by FACT-mediated nucleosome exchange stimulated by DNA-PK phosphorylation, by monoubiquitination at K119/K120 by RNF2-BMI1/RNF8 (promoting ATM and CHK1 activation) counteracted by Dub3 deubiquitinase, by Y142 dephosphorylation by EYA phosphatase that shifts the balance from apoptosis to repair, by SIRT1-mediated deacetylation at K5 that enables S139 phosphorylation, and by ADP-ribosylation at E141 that directs base excision repair; H2AX is required for G2-M checkpoint activation, prevention of aberrant DNA end resection in G1 lymphocytes, genomic stability during V(D)J recombination and class switch recombination, meiotic sex chromosome inactivation, and DNA ladder formation during apoptosis, while its expression level is post-transcriptionally controlled by miR-24 and miR-138, and its protein stability is regulated by a PRMT5-RNF168-SMURF2 proteostasis axis.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"H2AX is a histone H2A variant that serves as the central chromatin-based platform for the DNA damage response, undergoing rapid phosphorylation at serine 139 (forming γ-H2AX) by ATM, DNA-PK, or ATR kinases across megabase-scale chromatin domains shaped by three-dimensional chromosomal topology, thereby recruiting repair and signaling factors including 53BP1, MDC1, INO80, and BRCA1 [PMID:9488723, PMID:11571274, PMID:12697768, PMID:15607974, PMID:32572033]. γ-H2AX is resolved by context-specific phosphatases — PP2A after exogenous DSBs, PP4 after replication stress, and Wip1 as a general attenuator — while additional post-translational modifications including TIP60-mediated acetylation followed by UBC13-dependent ubiquitination, RNF2-BMI1/RNF8-mediated monoubiquitination at K119/K120, SIRT1-regulated K5 deacetylation, EYA-mediated Y142 dephosphorylation, and E141 ADP-ribosylation collectively tune the balance between DNA repair, checkpoint activation, and apoptosis [PMID:16310392, PMID:18614045, PMID:20460517, PMID:17709392, PMID:21676867, PMID:19234442, PMID:33264433, PMID:35258628]. Beyond canonical DSB repair, H2AX phosphorylation is required for G2-M checkpoint enforcement, prevention of aberrant CtIP-mediated end resection during V(D)J recombination, meiotic sex chromosome inactivation, oocyte quality surveillance, and DNA ladder formation during apoptosis and necroptosis [PMID:12447390, PMID:21160476, PMID:15589157, PMID:26509888, PMID:16818236, PMID:22972376]. H2AX protein levels are post-transcriptionally controlled by miR-24 during hematopoietic differentiation and by a PRMT5–RNF168–SMURF2 proteostasis axis [PMID:19377482, PMID:31533041].\",\n  \"teleology\": [\n    {\n      \"year\": 1998,\n      \"claim\": \"The discovery that DSBs induce rapid phosphorylation of H2AX at S139 across ~2 Mb chromatin domains established γ-H2AX as a large-scale chromatin mark for broken DNA, raising the question of which kinases are responsible and what downstream effectors are recruited.\",\n      \"evidence\": \"2D gel electrophoresis and 32P incorporation in irradiated mammalian cells and mice\",\n      \"pmids\": [\"9488723\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Kinase identity unknown\", \"Functional consequence of modification not yet tested\", \"Whether phosphorylation is strictly DSB-specific was not addressed\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Identification of ATM as the primary H2AX kinase after DSBs, with DNA-PK providing residual activity, answered the kinase-identity question and established that PIKK family members are the writers of γ-H2AX.\",\n      \"evidence\": \"In vitro kinase assay, ATM−/− and DNA-PKcs−/− cell lines, rescue by ectopic ATM expression\",\n      \"pmids\": [\"11571274\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"ATR contribution at replication forks not yet tested\", \"Relative contributions of ATM vs. DNA-PK in different damage contexts not resolved\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Demonstrating that H2AX−/− mice phenocopy ATM−/− cells for G2-M checkpoint failure at low DSB doses established γ-H2AX as a signal amplifier required for threshold-level checkpoint activation, not merely a damage marker.\",\n      \"evidence\": \"H2AX−/− and 53BP1−/− mouse knockouts, flow cytometry, 53BP1 foci immunofluorescence\",\n      \"pmids\": [\"12447390\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether H2AX contributes to S-phase or G1 checkpoints was unknown\", \"Mechanism of signal amplification not molecularly defined\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Direct binding of 53BP1 to phosphorylated (but not unphosphorylated) H2AX, combined with evidence that DNA-PK phosphorylates H2AX within nucleosomes enhanced by acetylation, established the first molecular link between γ-H2AX and effector recruitment and defined chromatin context as a regulatory layer.\",\n      \"evidence\": \"In vitro binding assays with H2AX phospho-mutant reconstitution; reconstituted nucleosomal kinase assays\",\n      \"pmids\": [\"12697768\", \"14627815\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"MDC1 as an intermediary adaptor not yet characterized\", \"Whether 53BP1 binding is direct to γ-H2AX or indirect through other marks was debated\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Showing that H2AX haploinsufficiency causes genomic instability and that phosphorylation-site mutants (S→A, S→E) fail to rescue H2AX-null phenotypes established H2AX as a dosage-dependent, phosphorylation-dependent tumor suppressor.\",\n      \"evidence\": \"H2AX+/−, H2AX−/−, p53−/− double-knockout mice with transgenic phospho-site mutant reconstitution and cytogenetics\",\n      \"pmids\": [\"12914701\", \"12914700\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific repair pathway(s) compromised by haploinsufficiency not identified\", \"Whether phosphomimetic failure reflects structural requirements beyond charge not tested\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"ATM and DNA-PK were shown to be redundant for IR-induced γ-H2AX (requiring ablation of both to eliminate signal), while the INO80 chromatin remodeling complex was identified as a γ-H2AX-dependent effector recruited to DSBs, expanding the reader network beyond checkpoint proteins to chromatin remodelers.\",\n      \"evidence\": \"ATM/DNA-PK double-deficient cells with epistasis analysis; Co-IP and ChIP of INO80 at HO-induced DSBs in yeast\",\n      \"pmids\": [\"15059890\", \"15607974\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether INO80 recruitment via γ-H2AX is conserved in mammals not shown\", \"SWR1/SRCAP remodeler contributions not yet addressed\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Discovery that ATR phosphorylates H2AX on the XY body in a BRCA1-dependent manner for meiotic sex chromosome inactivation extended γ-H2AX function beyond DNA repair to programmed chromatin silencing during gametogenesis.\",\n      \"evidence\": \"Immunofluorescence of ATR and γ-H2AX in wild-type vs. BRCA1-mutant spermatocytes\",\n      \"pmids\": [\"15589157\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How ATR-dependent γ-H2AX recruits silencing machinery was not identified\", \"Whether H2AX phosphorylation is sufficient for MSCI without other marks not tested\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Identification of PP2A as the phosphatase that dephosphorylates γ-H2AX after repair completion answered how damage foci are resolved and revealed that persistent γ-H2AX impairs repair and cell survival.\",\n      \"evidence\": \"Co-IP, in vitro phosphatase assay, PP2A RNAi causing persistent γ-H2AX foci and radiosensitivity\",\n      \"pmids\": [\"16310392\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether PP2A acts on nucleosomal γ-H2AX or requires eviction not tested\", \"Context-specificity relative to replication stress not addressed\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Demonstrating that DNA-PK (not ATM) phosphorylates H2AX during apoptosis, and that JNK-mediated H2AX phosphorylation is required for DNA ladder formation by CAD, established distinct kinase usage in apoptotic versus repair contexts and a pro-death effector role for γ-H2AX.\",\n      \"evidence\": \"DNA-PKcs−/− and ATM−/− cells in apoptotic conditions; H2AX−/− MEFs with in vitro CAD assay\",\n      \"pmids\": [\"16567133\", \"16818236\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How γ-H2AX facilitates CAD-mediated cleavage structurally was not defined\", \"Whether this applies to all apoptotic stimuli was not tested\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Elucidation of a sequential TIP60 acetylation → UBC13 ubiquitination cascade on H2AX that promotes its eviction from damaged chromatin revealed that γ-H2AX removal is an actively regulated process requiring ordered PTMs.\",\n      \"evidence\": \"In vivo acetylation and ubiquitination assays, TIP60/UBC13 Co-IP, dominant-negative and knockdown experiments\",\n      \"pmids\": [\"17709392\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific acetylation site on H2AX not mapped\", \"Whether eviction is required for repair completion or just foci resolution was unclear\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Identification of FACT as the H2AX nucleosome exchange factor stimulated by DNA-PK phosphorylation, PP4 as the replication-stress-specific γ-H2AX phosphatase, and Rvb1-TIP60 as the HAT complex required for γ-H2AX removal collectively established that γ-H2AX dynamics are governed by context-specific writer-eraser-remodeler modules.\",\n      \"evidence\": \"In vitro nucleosome exchange with purified FACT; PP4 phosphatase assay on mononucleosomes with replication-stress specificity; Rvb1 RNAi epistasis with TIP60\",\n      \"pmids\": [\"18406329\", \"18614045\", \"18285460\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How FACT discriminates H2AX-containing vs. canonical H2A nucleosomes not defined\", \"Whether PP4 and PP2A act on distinct pools simultaneously was not tested\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Discovery that EYA dephosphorylates H2AX Y142 to switch the γ-H2AX platform from apoptosis to repair, and that miR-24 post-transcriptionally silences H2AX during differentiation, established two new regulatory layers — a PTM-encoded fate switch and a microRNA-based expression control mechanism.\",\n      \"evidence\": \"In vitro EYA phosphatase assay, mass spectrometry for Y142, genetic epistasis; miR-24 3′UTR reporter with rescue by miR-24-insensitive H2AX\",\n      \"pmids\": [\"19234442\", \"19377482\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"WSTF kinase (Y142 writer) interaction with EYA not mechanistically dissected\", \"Whether miR-24 regulation is conserved beyond hematopoiesis not shown\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Showing that H2AX prevents CtIP-mediated aberrant end resection at RAG-generated hairpin ends in G1 lymphocytes revealed a cell-cycle- and context-specific protective function of γ-H2AX-MDC1 in enforcing faithful NHEJ during V(D)J recombination.\",\n      \"evidence\": \"H2AX−/− lymphocytes with CtIP/MDC1 genetic epistasis, V(D)J junction sequencing, cytogenetics\",\n      \"pmids\": [\"21160476\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether this protective mechanism extends to class-switch recombination junctions was not shown\", \"How γ-H2AX physically blocks CtIP access was not defined\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Identification of RNF2-BMI1 as the E3 ligase for H2AX K119/K120 monoubiquitination, required for ATM recruitment and full γ-H2AX signaling, established ubiquitination as a prerequisite for (not just consequence of) the DSB response.\",\n      \"evidence\": \"Co-IP, ubiquitination assay, K119R/K120R mutants, siRNA with DSB marker readouts\",\n      \"pmids\": [\"21676867\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether RNF2-BMI1 acts before or after initial S139 phosphorylation was not resolved temporally\", \"Relationship to RNF8/RNF168-mediated ubiquitin signaling not fully distinguished\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Demonstrating that AIF forms a nuclear DNA-degrading complex with γ-H2AX during necroptosis, dependent on ATM/DNA-PK-mediated S139 phosphorylation, established a role for H2AX in caspase-independent programmed cell death.\",\n      \"evidence\": \"H2AX−/− cells, kinase inhibitors, S139A/S139E mutant reconstitution, AIF-γ-H2AX Co-IP\",\n      \"pmids\": [\"22972376\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How AIF recognizes γ-H2AX specifically (binding interface) was not defined\", \"Whether this mechanism operates in vivo during pathological necroptosis not shown\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Identification of Dub3 as a deubiquitinase that directly removes ubiquitin from H2AX, counteracting RNF8/RNF168, and selectively suppressing 53BP1/BRCA1 foci without affecting MDC1 or γ-H2AX, revealed a deubiquitination-based mechanism for fine-tuning downstream effector recruitment.\",\n      \"evidence\": \"In vitro DUB assay, catalytically inactive Dub3 mutant, Co-IP, immunofluorescence\",\n      \"pmids\": [\"24704006\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether Dub3 acts on mono- or poly-ubiquitinated H2AX preferentially not determined\", \"Physiological context regulating Dub3 activity at DSBs unknown\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Genetic rescue of oocyte loss in XO mice by H2AX deletion or point mutation established γ-H2AX as a functional driver of oocyte elimination triggered by asynapsed chromosomes, extending H2AX function to meiotic quality control in females.\",\n      \"evidence\": \"H2AX−/− and point-mutant mice on XO background, oocyte counting, γ-H2AX immunofluorescence\",\n      \"pmids\": [\"26509888\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Downstream effectors linking γ-H2AX to oocyte apoptosis not identified\", \"Whether this mechanism applies to autosomal asynapsis was not tested\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Chronic oxidative stress was shown to promote RNF168-mediated poly-ubiquitination and proteasomal degradation of H2AX, while γ-H2AX signaling was found to drive chromosome territory relocation via nuclear myosin 1, revealing proteostatic vulnerability and a mechanical effector function of γ-H2AX.\",\n      \"evidence\": \"ROS modulation with RNF168 Co-IP and ubiquitination assays; H2AX-deficient cells with FISH and NM1 motor-dead mutants\",\n      \"pmids\": [\"27006338\", \"27365048\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether RNF168-dependent H2AX degradation is a general stress response or tumor-specific is unclear\", \"How γ-H2AX recruits NM1 mechanistically is not defined\", \"Single-lab findings for chromosome territory relocation\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Conditional MOF deletion in spermatocytes demonstrated that H4K16 acetylation by MOF is required for chromatin-wide γ-H2AX spreading during all three meiotic waves, distinguishing axis-restricted from chromatin-wide γ-H2AX as functionally distinct states.\",\n      \"evidence\": \"Germ cell-specific Mof knockout, chromosome spreading, γ-H2AX and MDC1 immunofluorescence\",\n      \"pmids\": [\"29795555\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether MOF acts by enabling ATR/ATM access or by facilitating MDC1 spreading not distinguished\", \"Applicability to somatic DSB-induced γ-H2AX spreading not tested\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"The PRMT5–RNF168–SMURF2 axis was identified as a proteostasis circuit controlling H2AX protein levels, where PRMT5 sustains RNF168 to stabilize H2AX while SMURF2 promotes its degradation, linking epigenetic enzyme activity to H2AX abundance.\",\n      \"evidence\": \"Co-IP, RNAi, protein stability assays in MTAP-deficient glioblastoma cells\",\n      \"pmids\": [\"31533041\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether SMURF2-mediated degradation is ubiquitin-dependent at the same sites as RNF168 mono-ub was not clarified\", \"Single-lab study in a specific genetic context (MTAP-deleted)\", \"In vivo validation lacking\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Hi-C-resolved mapping of γ-H2AX domains showed that spreading follows pre-existing 3D chromosomal contacts rather than linear distance, while ADP-ribosylation at E141 was discovered to direct BER and suppress erroneous DSB signaling, together refining the spatial and PTM logic of H2AX-based damage signaling.\",\n      \"evidence\": \"Hi-C + ChIP-seq at defined DSBs; mass spectrometry identification of E141 ADP-ribosylation with site mutant and Neil3 Co-IP\",\n      \"pmids\": [\"32572033\", \"33264433\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether cohesin or condensin mediate the contact-dependent spreading was not tested\", \"Which ADP-ribosyltransferase modifies E141 was not identified\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"SIRT1 was identified as the deacetylase for H2AX K5, and K5 acetylation was shown to impair S139 phosphorylation, establishing a crosstalk in which acetylation state gates the canonical γ-H2AX response.\",\n      \"evidence\": \"Cardiomyocyte-specific Sirt1 knockout, H2AX K5Q and S139A mutants, acetyl-K5 and phospho-S139 immunostaining\",\n      \"pmids\": [\"35258628\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The acetyltransferase that writes K5 acetylation was not identified\", \"Whether K5 acetylation inhibits kinase access or promotes phosphatase activity not distinguished\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include: the structural basis for how γ-H2AX recruits each specific effector (53BP1, MDC1, AIF); how the multiple PTMs on H2AX (S139-P, Y142-P, K5-Ac, K119/120-Ub, E141-ADP-ribose) are coordinated temporally and spatially in a single nucleosome; and whether the non-canonical roles of H2AX in stem cell proliferation and DNA demethylation represent generalizable mechanisms or context-restricted phenomena.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No cryo-EM or crystal structure of γ-H2AX nucleosome with bound effector\", \"Combinatorial PTM code on single H2AX molecules not resolved\", \"In vivo relevance of GABA receptor–H2AX axis and HMGA2–FACT–H2AX demethylation pathway requires independent replication\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0042393\", \"supporting_discovery_ids\": [0, 11, 19, 31]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0, 5, 12]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005694\", \"supporting_discovery_ids\": [0, 6, 7, 32, 36]},\n      {\"term_id\": \"GO:0000228\", \"supporting_discovery_ids\": [7, 35, 36]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0, 26, 33]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [0, 1, 2, 3, 5, 6, 8, 13, 14, 25, 29]},\n      {\"term_id\": \"R-HSA-4839726\", \"supporting_discovery_ids\": [0, 6, 11, 12, 19, 32, 36]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [3, 24, 25]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [9, 10, 26]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [17]},\n      {\"term_id\": \"R-HSA-1474165\", \"supporting_discovery_ids\": [7, 35, 36]}\n    ],\n    \"complexes\": [\n      \"nucleosome\"\n    ],\n    \"partners\": [\n      \"ATM\",\n      \"DNA-PKcs\",\n      \"ATR\",\n      \"MDC1\",\n      \"TP53BP1\",\n      \"TIP60\",\n      \"RNF168\",\n      \"SMURF2\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}